1. Field of the Invention
The invention relates to the use of water-soluble thickeners and more particularly relates to the use of high molecular weight, polyoxyalkylene water-soluble thickeners made using hydrophobic alcohols for glycol-water based hydraulic fluid applications.
2. Other Thickeners in the Field
Previous thickeners have been typically prepared by the reaction of mixtures of ethylene oxide and propylene oxide together with polyoxyalkylene glycol initiators to give materials having molecular weights greater than 5000. Typical ratios range from 2:1 to 4:1 in proportions of oxide mixture to initiator. Undiluted viscosities of the resultant products range between 100 centistokes and 2000 centistokes at 100.degree. F. Representative commercial fluids are the JEFFOX.RTM. synthetic functional fluids manufactured by Texaco Chemical Co.
An object of the invention is to produce water-soluble fluids with high viscosities by an economical manner. It is expected that the fluids would be particularly useful as thickening agents for fire-resistant glycol-water hydraulic fluids for use in refineries, coal mines, steel mills, machine shops, and military equipment.
Functional fluid uses as brake fluids, lubricants and starting materials for surfactants, plasticizers and resins are also anticipated.
High molecular weight polyether block polymers having high viscosities may be made by the sequential alkoxylation of a polyfunctional initiator with alkylene epoxide components according to U.S. Pat. No. 3,535,307 to Moss, et al. High molecular weight polyether polyols according to U.S. Pat. No. 3,829,506 to Schmolka, et al. are made by the copolymerization of low molecular weight alkylene oxides and .alpha.-olefin oxides containing from ten to twenty carbon atoms with low molecular weight compounds having two to six hydroxyl groups.
However, more pertinent to the instant invention are thickeners made using mono-hydric alcohols as initiators. For example, U.S. Pat. No. 2,174,761 to Schuette, et al. teaches that water-soluble products can be obtained by reacting an organic compound containing at least one hydroxy group in the molecule (such as propyl alcohol, amyl alcohol, benzyl alcohol, phenols, cresols, etc.) with an alkylene oxide having at least 3 carbon atoms and then effecting a "water-solubilizing step" which essentially involves adding an ethylene oxide "cap". Although the ethylene oxide cap may involve two to twenty moles of ethylene oxide per mole of alcohol, the higher alkylene oxide proportion is much reduced, on the order of 2 to 4 moles per mole of alcoholic initiator. The reaction of monohydric alcohols with alkylene oxides such as ethylene oxide or propylene oxide with the subsequent addition of a polyether-substituted chlorohydrin is revealed in U.S. Pat. No. 3,102,893 to Gaertner. Again, the mole ratio of alcohol to alkylene oxide is rather low: from less than 1:1 to 1:9.
Monohydric alcohols, such as methanol and butanol, but particularly glycols, may be reacted repeatedly with ethylene oxide and higher alkylene oxide groups to give a metal quenching medium having average molecular weights in the 600 to 40,000 range as seen in U.S. Pat. No. 3,220,893 to Blackwood, et al. U.S. Pat. No. 3,424,817 to Hicks teaches a process for preparing fusible polymeric polyhydroxy polyether resins by reacting a diepoxide resin and a monohydric alcohol in a mole ratio of about 1:1. See also U.S. Pat. No. 3,374,286 to Hicks where a monoepoxide replaces the diepoxide. Further, U.S. Pat. No. 3,538,033 to Hayashi, et al. reveals that polyoxyalkylene compounds having thickening properties may be prepared by reacting a diepoxide with a monohydric aliphatic alcohol (such as octadecyl alcohol) or an alkyl phenol (such as nonylphenol or dinonylphenol) which has at least 12 carbon atoms and with which has been reacted an alkylene oxide in a number of moles not less than 20.
Thickeners for aqueous liquids may also be obtained by capping a liquid straight chain polyoxyalkylene compound derived from ethylene oxide or ethylene oxide and one lower alkylene oxide with at least one active hydrogen-containing initiator having only one active hydrogen atom, according to U.S. Pat. No. 4,288,639 to Camp. The initiator is preferably a monohydric alcohol having 12 to 18 carbon atoms and the capping agent is an alpha-olefin oxide having preferably 12 to 18 carbon atoms.
Particularly relevant to the invention at issue is U.S. Pat. No. 3,379,644 to Katzenstein which discloses ethoxylated long chain alkylated phenols as thickening agents useful in hydraulic fluids. However, this patent only teaches a rather limited range of molar ratio of ethylene oxide to alkylated phenol, namely 12:1 to 18.5:1. In addition, this patent teaches that as the ethylene oxide content increases, the viscosity of the resultant thickener decreases (compare Example IV and Example V). Also of interest is U.S. Pat. No. 2,425,755 to Roberts, et al. which teaches that ethylene oxide and propylene oxide may be added to low molecular weight alcohols (ten or less carbon atoms) to give viscous materials useful as hydraulic fluids without water-glycol dilution.